Recently, mobile communications systems aiming at seamless connection with cable systems have drawn attention. At the same time, in view of efficient frequency use there is also a movement toward letting a variety of systems share the same frequency band in common as shown in FIG. 41, instead of permitting one system to occupy one specific frequency.
With this trend, there have been attempts to put Internet connection, MPEG2 data transmission, DV (digital video) signal transmission and other various communications systems into practice within the same frequency band.
However, since when these different systems are handled using wireless transmission, the required QoS (quality of service) differs from others depending on each system, there may be differences in the physical layer (modulation scheme, interleaver, error correction coding, etc.,), MAC (media access control) layer (differences in frame length and frame structure) and others, as shown in FIG. 42. Accordingly, in order to demodulate these different systems correctly, it is necessary to identify each system after the data has been demodulated.
For this reason, the conventional technologies use methods whereby, no matter whether a signal is needed or not, the signal has to be once demodulated in its physical layer and MAC layer, and then if the data is determined to be a desired one, the demodulation is continued, or cancelled otherwise.
However, the above prior art technologies have suffered the problems that it takes time to identify the service (system) and also extra consumption of power is needed to demodulate unnecessary signals.
The present invention has been achieved in view of the above problems, it is therefore an object of the present invention to provide a wireless communication transmitter and a wireless communication receiver which can detect an arrival of a signal of the desired system, simply and precisely at an early stage, from a plurality of systems sharing the same frequency band.